Amplifier circuits



March 1936- I H. BARTELS v 2,035,289 I i AMPLIFIER CIRCUITS Filed Feb. 17, 1933 INVENTOR.

HANS-51457115 ATTORNEY Patented Mar. 24, 1936 2,035,289 AMPLIFIER ornourrs,

Hans Bartels, Berlin, Germany, assignor to Teleiunken' Gesellschaft fiir 'Drah'tlose Tele tion of Germany gra'phie m. b.H.', Berlin, Germany; a'corpora- Application February 17, 1933.; Serial 1Io.'657,173, In Germany April1'1,1932

3 Claims.

In high frequency and audio frequency amplifiers it is often the case that linear and nonlinear distortions occur. The cause of these distortions is often due to production of currents in otherwise currentless circuits on account of which the voltage is the output circuits is no longer proportional to the input voltage. Hitherto it has been attempted to render such distortions inefiective by correspondingly over-sizing the tubes, in other words, by taking care in the design and use of tubes that the grid current is as small as possible.

The present application shows a manner of reducing, or preventing, respectively such distortions by which a considerably more favorable utilization of the preliminary tube and end tube is obtained. Contrary to the hitherto known arrangements an additional circuit is used acting against the distortions, and in turn controlled by the current which produces the distortions so that it is only effective at the moment in which the distorting current develops.

In order that the invention may be more readily understood, several modes of execution are described in the following by way of example.

Fig. 1 shows one embodiment,

Fig. 2 shows a modification.

In Fig. 1, I and 2 designate two amplifier tubes connected in cascade. 3 is the input transformer; 4 the intermediate transformer and 5 designates the output transformer. The output resistance or load is shown at 6. 1 represents a resistor inserted in the grid circuit of the end tube 2 and 8 is a coupling transformer which couples the grid circuit of tube 2 with the anode circuit. 9 is an additional circuit element, as a tube, for instance, an amplifier.

If in the ordinary amplifier circuits not compris ing these compensating elements 1, 8 and 9, the tube 2 is operated in such manner that an appreciable grid current passes through the tube, then during periods in which current flows in the grid circuit, the anode current of the tube 2 will no longer be proportional to the voltage applied to the grid of tube I. The reason for this is, on the one hand, the influence on the anode current by the grid current appearing in the tube, and, on the other hand, the influence on the voltage of the preliminary tube due to the load caused by the grid circuit of the tube 2.

In accordance with the present invention the resistance 1 is placed in the grid circuit, which has no efiect as long as this circuit is not passed by a current, but in the moment, however, in which a current flows through the grid circuit a compensated. linear and non-linear distortions respectively are voltage drop is produced at this resistance. This voltage drop, thus proportional to the distorting current, is coupled across an additional element, such as an amplifier, and across the coupling transformer 8 with the output circuit of the tube 2 in such manner that the anode loss which would occur without this auxiliary circuit, is just Thus, the otherwise appearing eliminated. By means: of this auxiliary circuit it is possible to considerably increase the efficiency of the preliminary tube and end tube without causing unallowable distortions.

Furthermore itis the same whether a voltage proportional to the distorting current is tapped from an impedance in the grid circuit or whether in addition this voltage is tapped from another part of this circuit as for instance from the grid of the tube 2 proper.

For obtaining this advantage in accordance with the invention 'it is obviously within the scope of the invention if instead of the above described manner the voltage necessary for the compensation is obtained in another way, since the essential feature of the invention resides in the fact that the current producing the distortion is again utilized for the direct compensation of the distortions.

In Fig. 2 another method is shown. All of the circuit elements are designated by the same reference numerals as in Fig. 1 with the exception that the coupling transformer 8 is not coupled with the anode circuit of tube 2 as showvn in Fig. 1, but with the grid circuit of tube l and that the additional element 9 is dispensed with. When a current flows in the grid circuit of tube 2 of this arrangement, which distorts the anode current of tube 2, a voltage drop is again produced at the auxiliary resistor l and which is now coupled with the grid circuit of the preliminary tube l across the coupling transformer 8' in such a manner that due to this additional voltage the distortions of the anode current of tube 2 are just compensated.

As is obvious, it is possible to directly apply the described method during the construction of three or multi-electrode tubes, and to combine the necessary circuit elements with the tube while the same is being built.

While I have indicated and described one system for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by nomeans limited to the particular organization shown and described, but that many modifications may be made without departing from the scope of my invention as set forth in the appended claims.

What is claimed is:

1. Radio apparatus comprising an amplifying stage including input and output circuits, an element in one of said circuits only, said element being adapted to be traversed by currents depending on distortion in said system, and means for applying a potential having a definite relation to the flow of currents through said element, to a part of said system where it will compensate for the distortion,

2. Radio receiving apparatus including an amplifying stage, input and output circuits for said amplifying stage, a resistor in a part of said input circuit which is not common to said output circuit, and means for applying a potential having a definite relation to the potential difference across the terminals of said resistor due to the flow of grid current in said circuit, to the output circuit to correct for the distortion resulting from the said flow of grid current.

3. A radio frequency amplifying stage including an amplifier tube, input and. output circuits therefor, an impedance element connected to be traversed by grid current flowing in said amplifying stage, said impedance element being connected in a part of said input circuit which is external to said output circuit, and means for impressing potential on the output circuit of said amplifying stage proportional to the flow of grid current.

HANS BARTELS. 

